1. Field of the Invention
The present invention is directed to providing localized cooling of wall sections for furnaces and in particular to a water cooled panel for use in an electric arc furnace.
2. Description of the Prior Art
Arc furnaces are commonly used for producing steel and other metals and alloys. Historically, arc furnaces, and in particular electric arc furnaces, have been constructed of a steel structure and have a refractory material lining typically in the form of a bowl. The electric arc furnace has a set of electrodes which carry an electrical current used to melt material, such as scrap metal or pelletized iron sponge, which is turned into molten metal. The arc furnace is typically constructed such that new material to be melted can be continuously added and the molten metal can be drawn off at a continuous rate. U.S. Pat. No. 4,617,673, to Fuchs et al., discloses an example of this type of an electric arc furnace.
In order for the arc furnace to melt the material into molten metal, the electrical current arcs from the electrodes to the metal and back thereby raising its temperature and melting the material. Temperatures in the arc furnace can typically reach several thousand degrees Celsius. These relatively hot temperatures result in excessive wear of the refractory brick material as well as the furnace structure resulting in relatively rapid deterioration of the furnace. This rapid wearing of the furnace walls becomes extremely significant and very costly considering that the furnace must be shut down and allowed to cool before the excessively worn areas of the walls and roof can be repaired. Typically, current furnace wall and roof assemblies only last a short time before they must be repaired or replaced.
These problems have led to significant efforts and attempts to provide varying types of arc furnace wall and roof constructions which cost less and have an extended life. These efforts have led to advances which have focused upon providing devices which can either cool the refractory material of the furnace or completely replace it with a material which can withstand such temperatures. The advances have been along several lines. In particular, different materials have been used and different devices developed for cooling the wall and roof in an attempt to extend the useful life of the side and roof panels of the furnace.
In order to prolong the useful life of the furnace walls and roof, it is well known to provide a means for protecting the walls and roof from heat and also to draw off excess heat. With respect to cooling the wall and roof, many designs have been proposed which purport to solve certain problems with prior art designs, however, while some of the prior art designs have extended the useful life of the furnace walls and roof, there is still a great need to further extend their useful lives, while simultaneously providing a design which is overall less costly and easy to manufacture.
It is well known in the art to provide a cooling panel connected to the wall or roof of the furnace to remove the excess heat therefrom. These cooling panels can take many different forms and can operate upon different principles. It is also well known to circulate a cooling fluid in a serpentine path through machined channels in a hollowed wall. Several United States patents directly disclose the idea of using machined passages formed in a panel and having cooling water circulated therethrough to provide a means of cooling the panel. In particular, U.S. Pat. No. 4,453,253, to Lauria et al., discloses an arc furnace constructed using graphite blocks having panels containing machined serpentine conduits for circulating a cooling fluid to remove heat from the graphite block; these panels are attached to the outer surface of the furnace. Lauria et al. teach that by using liquid cooled graphite blocks the useful life of the furnace wall is extended due to the insulative properties of graphite. Lauria et al. further disclose that the outer surface cooling panel attached to the block is preferably made of a metal with the particular machining construction of the conduits being a matter of choice and that the cooling panel may be attached to the graphite block using bolts, cement or the like, individually or collectively. Lauria et al. further teach that graphite, unlike metal, will not burn through if arcing occurs on the hot face of the furnace wall.
U.S. Pat. No. 4,207,060 to Zangs also discloses a machined cooling wall for a furnace formed of a cooling pipe coil in which cooling water is circulated and is used to cool the heat resistant interior wall of an arc smelting furnace. Similar to Zangs, U.S. Pat. No. 4,637,034 to Grageda also discloses a machined water cooling panel for use in a metallurgical furnace. Grageda discloses that the panel is formed using parallel pipes connected at their ends to headers or a box-type cooler formed of steel plates or sheet steel. The parallel pipes are arranged to define a serpentine path for the cooling fluid. Grageda discloses that fluid orifices are provided to permit a minor amount of flow through the baffle near the cut-backs of the serpentine path to prevent water from stagnating and creating a hot spot or steam bubble in the wall. Additionally, U.S. Pat. No. 4,273,949, to Fischer et al., discloses an arc furnace roof made of segments having cooling fluid inlet and outlets therein for circulating cooling fluid through the roof panels of the furnace. Fischer et al. teach that by circulating cooling fluid in the roof panels the necessity of lining the associated segments with refractory lining is eliminated.
While all of the above references have improved the overall level of the art with respect to providing various alternatives which help to extend the useful life of the walls and roof of a furnace and therefore also the time between shut downs of the furnace, none of these references disclose or teach a device which has a high thermal conductivity, can be produced at a relatively low cost with a minimum of manufacturing effort out of a single material, and significantly extends the useful life of the furnace resulting in significant cost savings because of reduced manufacturing costs and down time.
Thus, there is still a considerable need to provide a cooling panel for use in a wall or roof of an electric arc furnace which can be produced at a relatively low cost and which has a significantly longer useful life than known cooling panels.